Low foam surfactants



Patented Nov. 10, 1970 3,539,518 LOW FOAM SURFACTANTS George C.Feighner, Franklin Lakes, N.J., and Dean R. W e1mer, Ponca City, Okla,assignors to Continental Oil Company, Ponca City, Okla., a corporationof Delaware No Drawing. Filed Feb. 21, 1968, Ser. No. 707,326 Int. Cl.Clld N66 US. Cl. 252-89 10 Claims ABSTRACT OF THE DISCLOSURE Low foam,nonionic surfactant compositions consisting essentially of lower (Cstraight chain acyl group capped alcohol ethoxylates. More specifically,the surfactant compositions consist essentially of analkoxypolyethenoxycarboxylate compound of the general structural formula0 Rr-o oH2oH2o d-R2 where R, is a C -C n-alkyl group attached to theoxygen atom through a primary or secondary carbon atom, n is a numberfrom 5 to 25, inclusive, and R is selected from the group consisting ofhydrogen and n-alkyl groups containing from 1 to 5 carbon atoms.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to nonionic surfactants having low foaming power, and thus beniguseful in cleaning applications where excessive foam is undesirable.

Brief description of the prior art In some industrial and householdcleaning operations, it is very desirable or necessary to maintain a lowlevel of foam during the cleaning operation. For example, in theindustrial field, conventional nonionic surfactants usually producefoaming to an extent rendering them unsuitable in spray metal cleaningformulations. In the household, conventional nonionic surfactants givetoo high a foam level for satisfactory use as the active ingredient indetergents and rinse aids for mechanical dishwashers. Excessive foam isobjectionable here because it may cause overflow of the machine, andeven moderate amounts of foam will interfere with proper rinsing. Lowfoaming can often be achieved by the addition of defoaming agents, butthis approach generally does not give adequate wetting or detergencyproperties.

A type of nonionic surfactant which has been previously proposedincludes the fatty acid esters of alcohol ethoxylates, which esters areproduced by condensing ethylene oxide with detergent range alcohols, andthen reacting such ethoxylated alcohols with fatty acids containing from8 to 18 carbon atoms, or with the chlorides of such acids. Estersproduced in this manner are described in US. Pat. 1,970,578 toSchoeller, issued Aug. 21, 1934, as possessing excellent wetting,foaming and cleansing powers. The Schoeller patent thus indicates thatthese C -C fatty acid derivatives are actually good foam producers, andthus provides no suggestion that they would have any utility whatsoeverin a cleaning usage where suppression of foam is important. Further thanthis, I have determined that the fatty acid capped alcohol ethoxylatesdescribed by Schoeller are of low water solubilitya characteristic whicheffectively prevents their being practical for use in applications wherean aqueous solution of the surfactant is required, and specifically, inthe dishwashing and industrial metal cleaning operations described.

OBJECTS OF THE INVENTION The present invention has as its basicobjective, the provision of new low foam, nonionic, surfactantcompositions. Subsidiary to this basic objective, further objectives ofthe invention are to demonstrate:

(a) That these compositions produce relatively low foam over a widetemperature range, and compare well in this respect with presently used,commercially available, 10W foam nonionic surfactants;

(b) That these compositions compare well with commercially available,low foam, noninic surfactants in wetting characteristics; and

(c) That the alkoxypolyethenoxycarboxylate compounds constituting theactive surfactant compounds used in the compositions are characterizedby relatively high water solubility, and have better cloud pointproperties than similar carboxylates derived from higher molecularweight carboxylic acids, and also commercially available nonionic, howfoam, surfactants.

SUMMARY OF THE INVENTION The present invention is broadly directed tonew surfactant cleaning compositions, and more specifically, tosurfactant compositions consisting essentially of water and acyl groupcapped alcohol ethoxylates of the structural formula where R, is a C -Cn-alkyl group bonded to the oxygen atom through a primary or secondarycarbon atom, n is a number from 5 to 25, inclusive, and R is selectedfrom the group consisting of hydrogen and n-alkyl groups containing from1 to 5 carbon atoms.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The acyl groupcapped alcohol ethoxylates of the invention which have the structuralFormula (1) set out above are prepared by initially reacting primary orsecondary monohydric n-alkanols with ethylene oxide in the presence ofan acidic or basic catalyst. Catalysts suitable for this reaction arewell known in the art and include, for example, alkali metal oxides andhydroxides, boron trifluoride, stannic chloride and sulfuric acid.Preferably, a basic catalyst is used in this ethoxylation reaction, andmost referably, from about 0.1 to about 0.3 weight percent of NaOH isutilized, based on the weight of the alcohol. The ethoxylation reactionis carried out under anhydrous conditions to avoid formation ofby-products, and at a temperature which is preferably in the range offrom about 310 C. to about 390 C. The reaction may be carried out atsubstantially atmospheric pressure, although it is preferably carriedout in an autoclave at pressures of from about 10 p.s.i.g, to aboutp.s.i.g. The amount of ethylene oxide introduced to the reaction zone,and the duration of reaction time, determines the number of moles ofethylene oxide added to the alcohol.

The alcohol ethoxylates can be capped with a suitable acyl group byreacting them with C -C straight chain alkanoic acids, or with the acylhalides or the anhydrides of such acids. Suitable acids include formic,acetic, propanoic, butyric, pentanoic, and hexanoic acids, and typicalhalides and anhydrides include acetyl chloride and acetic anhydride. Aconventional esterification reaction of the acid, or acid derivativewith the alcohol ethoxylate is carried out.

As previously indicated, the alkyl group (R in the structural Formula 1contains from four to twenty carbon atoms, and is thus derived fromalcohols ranging from n-butanol to n-eicosanol. Preferably, the alkylgroup of the capped ethoxylate contains from 8 to 16 carbon atoms, andmost desirably from 8 to 12 carbon atoms, depending, however, to someextent, upon the character of the remaining portion of the molecule ashereinafter explained. The surfactant compositions of the invention mayvery conveniently contain a mixture of acyl group capped ethoxylatesderived from the ethoxylation of mixtures of C to C n-alkanols of evencarbon number, since alcohol mixtures of this type are readily availablestarting materials.

The number of moles (designated n in the structural formula) of ethyleneoxide which are incorporated in the alkoxypolyethenoxycarboxylatecompounds during ethoxylation can range from to 25, but is preferablyfrom about 5 to about 12, and most desirably from about 5 to about 10.In order to achieve the requisite degree of water solubility in thesurfactant compounds, the carboxyl group of the compound should containfrom 1 to 6 carbon atoms and preferably contains from 2 to 4 carbonatoms.

The overall molecular structure which is most suitable for the cappedethoxylate compounds of the invention is dictated by the interaction ofthe several functional groups in the molecule, and the effect of eachgroup on such properties as water solubility, foaming characteristics,product color and biodegradability. With respect to water solubility, itis desirable that a 1 weight percent aqueous solution of the acyl groupcapped ethoxylates have a cloud point of at least 75 F., and mostperferably 100 F., with a higher cloud point being indicative of greatersolubility. Lengthening of the alcohol chain (in structural Formula 1,the R group) decreases water solubility whereas increasing the number ofethenoxy groups in the molecule increases solubility. Increasing thechain length of the carboxylic acid used in the esterification reactionso that the group R in the structural formula contains more carbon atomsalso has the effect of decreasing solubility. Increasing the number ofcarbon atoms in the R alkyl group derived from the alcohol also has theeffect or increasing the foam developed or sustained by the surfactant,whereas an increase in the number of incorporated ethenoxy groups tomuch above 12 groups tends to lessen the biodegradability of thecompounds.

Considering these criteria, an optimum balance of water solubility, lowfoaming, and biodegradability properties is attained in cappedethoxylate compounds in which the R n-alkyl group contains from 8 to 12carbon atoms, from 6 to ethenoxy groups (55 to 65 weight percent) areincluded, and the R group contains from 1 to 3 carbon atoms (that is, itis derived from acetic, propanoic or butyric acid). An increase in thenumber of carbon atoms in either R or R is preferably accompanied by anincrease in the number of ethenoxy groups in the molecule.

EXAMPLE 1 In order to provide a more complete appreciation of theproduct evaluation test data hereinafter appearing, the manner in whichthe tested compounds were prepared will be described. An alcohol mixturecontaining 85 weight percent normal l-decanol, about 8.3 weight percentnormal l-dodecanol, and about 6.7 weight percent normal l-tetradecanolwas ethoxylated in the manner hereinbefore described, using a sodiumhydroxide catalyst. A product was yielded which contained about 60weight percent ethylene oxide (an average value of 5.7 moles of ethyleneoxide per mole of alcohol). The sodium hydroxide catalyst was thenneutralized with glacial acetic acid, and the ethoxylated alcoholsisolated.

196.4 grams (0.5 mole) of the mixture of ethoxylated alcohols preparedin the manner described in the preceding paragraph were then charged toa 3-necked, creased flask equipped with a stirrer, thermometer, refluxcondenser and dropping funnel. 39.2 grams /2 mole) of acetyl chloridewere charged to the dropping funnel. The acetyl chloride was drippedinto the ethoxylate, maintaining a maximum temperature in the flask of45 C. After the acetyl chloride addition, the product was poststirredand blown with nitrogen for 25 minutes to remove the residual hydrogenchloride. The product ester was a cloudy, viscous liquid with a meltingpoint below 36 F.

The following examples demonstration the properties of the acyl cappedethoxylates which make them excellent surfactants for incorporation incompositions used for cleaning applications which require minimum foam,good water solubility and good wetting ability.

EXAMPLE 2 The product made in Example 1 was evaluated for foamproperties in a Hamilton Beach mixer test, conventionally used in theart to evaluate surfactant foam characteristics. For purposes ofcomparison, several commercially available, widely used, low foam,nonionic surfactants were subjected to the same malt mixer foam test.200 ml. of a 0.1 weight percent aqueous solution of the surfactants tobe tested were placed in a 1000 ml. tall form beaker, and the solutionsubjected to high speed stirring for three minutes. The tested solutionwas then allowed to settle for two minutes, and the height of the foamwas then measured. The tests were run at temperatures of F. and 140 F.The results of the tests are shown in Table I.

TABLE I Foam height at- 75 F., 140 F., Surfactant in cm. in cm.

Example 1 product 1. 2 0. 5 Commercial product A 1.0 0, 6 Commercialproduct B 2 2. 7 0.8

l A chlorine capped ethoxylated n-decanol containing 73 weight percentethylene oxide.

2 A chlorine capped ethoxylated n-decanol containing Weight percentethylene Oxide.

The data in Table I show that the surfactant product of Example 1compares favorably with the commercial, low foam, nonionic surfactantstested. In the Hamilton Beach test, foam heights of less than 5 cm. areconsidered low.

EXAMPLE 3 The product prepared in Example 1 was subjected to a cottonskein wetting test to obtain the 25 second wetting concentration, andthe wetting time required to wet he skein to a 0.1 percentconcentration. Data on one commercially available, low foam, nonionicsurfactant is included for purposes of comparison. The results obtainedare set forth in Table II.

TABLE II 25 second wetting Wetting concentime tration, to 0.1%,Surfactant percent sec.

Example 1 product 0. 063 9. 8 Commercial product A from Example 2 0. 06812. 3

The data appearing in Table II show that the product made in Example 1is a better wetting agent than the low foaming, nonionic, commerciallyavailable surfactant compared therewith.

EXAMPLE 4 ing capped ethoxylates were then evaluated for watersolubility by preparing 1 percent aqueous solutions of each of theproducts, and running cloud point tests upon each of the aqueoussolutions. The results of the cloud point tests are set forth in TableIII.

TABLE III Cloud point of Surfactant: 1% solution, F. Acetyl cappedethoxylate 137 Butyryl capped ethoxylate 81 Octanoyl capped ethoxylate34 The solubility evaluation of the three products showed, as evidencedby the data in Table III, that the octanoyl capped ethoxylate had verypoor solubility and thus would be undesirable for use as a low foam,nonionic employed in aqueous solutions. The acetyl capped ethoxylate, onthe other hand, demonstrated excellent water solubility.

Although certain preferred embodiments of the invention have been hereindescribed and illustrated by example, various departures from thespecific uses mentioned, and compound structures described, may beeffected without a consequent departure from the basic principles of theinvention. Changes and innovations of this type are therefore deemed tobe within the spirit and scope of the invention except as they maynecessarily be excluded therefrom by the appended claims or reasonableequivalents thereof.

What is claimed is:

1. A low foam, nonionic, surfactant composition consisting essentiallyof an acyl group capped alcohol ethoxylate having the structural formulawhere R is a C -C n-alkyl group attached to the oxygen atom through aprimary or secondary carbon atom, n is a number from 5 to 25, inclusive,and R is selected from the class consisting of hydrogen and n-alkylgroups containing from 1 to 5 carbon atoms.

2. A low foam, nonionic, surfactant composition as defined in claim 1wherein said composition contains an aqueous solution of said cappedethoxylates.

3. A low foam, nonionic, surfactant composition as defined in claim 1wherein the capped ethoxylates in said composition are characterized inhaving a water solubility such that a 1 Weight percent aqueous solutionof each of said capped ethoxylates has a cloud point of at least F.

4. A low foam, nonionic, surfactant composition as defined in claim 2wherein said composition consists essentially of a plurality of saidcapped ethoxylates, and wherein R contains from 8 to 16 carbon atoms.

5. A low foam, nonionic, surfactant composition as defined in claim 2wherein R contains 1 to 3 carbon atoms.

6. A low foam, nonionic, surfactant as defined in claim 2 wherein n isnot greater than 12.

7. A low foam, nonionic, surfactant composition as defined in claim 4wherein R contains from 8 to 12 carbon atoms,

8. A low foam, nonionic, surfactant composition as defined in claim 7wherein R contains from 1 to 3 carbon atoms,

9. A low foam, nonionic, surfactant composition as defined in claim 8wherein n is a number from about 6 to about 10.

10. A low foam, nonionic, surfactant composition as defined in claim 7wherein n is a number from about 6 to about 10.

References Cited UNITED STATES PATENTS 5/1938 Graves. 5/1963 Guest etal.

US. Cl. X.R. 260488, 496

